Prediction of Human Pharmacokinetics of Fomepizole from Preclinical Species Pharmacokinetics Based on Normalizing Time Course Profiles.

Fomepizole is used as an antidote to treat methanol poisoning due to its selectivity towards alcohol dehydrogenase. In the present study, the goal is to develop a method to predict the fomepizole human plasma concentration versus time profile based on the preclinical pharmacokinetics using the assumption of superimposability on simulated time course profiles of animals and humans. Standard allometric equations with/without correction factors were also assimilated in the prediction. The volume of distribution at steady state (Vss) predicted by simple allometry (57.55 L) was very close to the reported value (42.17 L). However, clearance (CL) prediction by simple allometry was at least 3-fold higher to the reported value (33.86 mL/min); hence, multiple correction factors were used to predict the clearance. Both brain weight and maximum life span potential could predict the CL with 1.22- and 1.01-fold difference. Specifically, the predicted Vss and CL values via interspecies scaling were used in the prediction of series of human intravenous pharmacokinetic parameters, while the simulation of human oral profile was done by the use of absorption rate constant (Ka) from dog following the applicability of human bioavailability value scaled from dog data. In summary, the findings indicate that the utility of diverse allometry approaches to derive the human pharmacokinetics of fomepizole after intravenous/oral dosing.

Prediction of Human Pharmacokinetics of Ulixertinib, a Novel ERK1/2 Inhibitor from Mice, Rats, and Dogs Pharmacokinetics.

BACKGROUND AND OBJECTIVES: Ulixertinib (BVD-523) is a novel and selective reversible inhibitor of ERK1/ERK2. The primary objectives of the study were to evaluate the pharmacokinetics of ulixertinib in mice, rats, and dogs followed by prediction of human pharmacokinetic profile by allometric equations with/without correction factors. METHODS: Oral and intravenous pharmacokinetic profiles of ulixertinib were generated in mice, rats, and dogs. The human intravenous pharmacokinetics profiles [volume of distribution (Vss) and clearance (CL)] were predicted employing simple allometry and using correction factors [maximum life span potential (MLP) and brain weight (BW)]. Pharmacokinetic data obtained from dogs were used to simulate human oral profile [area under the curve (AUC) and maximum plasma concentrations (Cmax)]. RESULTS: Post-intravenous administration the CL was moderate in dogs (15.5 mL/min/kg) and low in mice (6.24 mL/min/kg) and rats (1.67 mL/min/kg). Vss was 0.56, 0.36, and 1.61 L/kg in mice, rats, and dogs, respectively. The half-life (t½) of ulixertinib ranged between 1.0 and 2.5 h across the animal species. Following oral administration ulixertinib attained maximum concentration in plasma (Tmax) within 0.50-0.75 h in mice and rats, indicating that absorption was rapid; however, in dogs, Tmax attained at 2 h. Absolute oral bioavailability in mice and rats was > 92%; however, in dogs, it was 34%. By different allometric approaches, simple method and brain weight correction factor shown clear improvement in the prediction efficiency of allometric scaling for Vss (1.34-1.70 L/kg) and CL (4.18-6.09 mL/min/kg), respectively, comparing with the MLP method and simple method for CL. Similarly, simulation of oral human profile was attained from scaled values and dog data to predict reported human profile (AUC and Cmax). CONCLUSIONS: The derived pharmacokinetic parameters (AUC and Cmax at 600 mg dose) and simulated plasma concentration-time profiles of ulixertinib in humans were predicted with good confidence by allometric approach.

LC-ESI-MS/MS determination of 4-methylpyrazole in dog plasma and its application to a pharmacokinetic study in dogs.

A simple, specific, sensitive and rapid LC-ESI-MS/MS method has been developed and validated for the quantification of 4-methylpyrazole in dog plasma using N-methylnicotinamide-d4 as an internal standard (IS) as per regulatory guidelines. Sample preparation was accomplished through a simple protein precipitation. Chromatographic separation of 4-methylpyrazole and the IS was performed on a monolithic (Chromolith RP18e ) column using an isocratic mobile phase comprising 0.2% formic acid in water and acetonitrile (20:80, v/v) at a flow rate of 1.0 mL/min. Elution of 4-methylpyrazole and the IS occurred at ~1.60 and 1.56 min, respectively. The total chromatographic run time was 3.2 min. A linear response function was established in the concentration range of 4.96-4955 ng/mL. The intra- and inter-day accuracy and precision were in the ranges 1.81-12.9 and 3.80-11.1%, respectively. This novel method has been applied to a pharmacokinetic study in dogs.